I had the same Error 4 display message. I looked on YouTube and learned how to remove the unit from the dash. Very easy to do. I then removed the top cover with a Philips screw driver, maybe 12 screws. Then the tricky part. There are 4 small springs, 1 on each corner holding the top plate which secures the CDs. Unhook them (bent paper clip and magnifying glass a must). Don't drop them! Lift the plate off and then 1 by 1 remove the CDs. Reattach the top plate, put the cover back on, put the unit back in the dash. As someone else suggested, load only 5 CDs not 6. Cost? $0.00. Patience and perseverance definitely needed. Worked for me.
